Composite expansion joint material

ABSTRACT

A flexible composite expansion joint material comprises a fluoropolymer containing woven fabric substrate with mutually perpendicular warp and fill yarns. The substrate is subdivided into plural segments which are arranged successively in a longitudinally extending assembly with the warp and fill yarns of each segment extending obliquely with respect to the assembly length. At least one other component extends over the assembly length. The successively arranged substrate segments are spliced together and integrally joined to the other component by lamination under conditions of elevated temperature and pressure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to composite materials employed in thefabrication of nonmetallic expansion joints, in particular those servingas flue duct seals in low pressure high temperature gas serviceinstallations.

2. Description of the Prior Art

Nonmetallic expansion joints are used in both liquid service and gasservice installations.

Liquid service expansion joints must be capable of operating under wideranges of pressure and temperature, e.g., pressures ranging from fullvacuum to 150 p.s.i. and higher, and temperatures ranging from below 0°F. to 300-400° F. Such expansion joints are predominantly manufacturedfrom single ply materials supplied in roll form as “roll goods”, e.g.,rubber and woven fabrics. Expansion joint manufacturers typically employmolding and hand lay up techniques to produce composites of suchmaterials with relatively thick cross sections on the order of 0.5inches. The resulting expansion joints are very stiff, thereby requiringsignificant forces to generate any movement or flexing.

In contrast to the foregoing, gas service expansion joints, morecommonly referred to as “flue duct seals”, are designed to operate underrelatively low pressure conditions, typically ±5 p.s.i., and attemperatures ranging from below 0° F. to 1400° F. and higher. Thecomposite materials used in the manufacture of flue duct seals can haverelatively thin cross sections on the order of 0.006 to 0.25 inches,typically including a single ply of woven fabric combined with bothrubbers and perfluoroplastics. Thicker constructions include additionalwoven fabric lies. Such composite materials are usually manufactured bycoating or laminating techniques and are also supplied as roll goods toexpansion joint manufacturers. Ideally, these composite materials shouldbe inherently flexible, and capable of readily elongating underrelatively low stress conditions.

The woven fabrics used as the load bearing components of expansion jointcomposites are commonly “square weaves”. Such fabrics are high modulusmaterials that do not readily stretch or elongate when stressed in thedirection of their warp or fill yarns. However, the same materials arecapable of readily stretching if they are arranged with their yarns on abias with respect to the direction of stress. Thus, in situations wherethe ability to readily stretch or elongate is critical, as is often thecase in the expansion joint industry, expansion joint manufacturers haveresorted to relatively complex and labor intensive fabricationtechniques in order to achieve a bias orientation of the conventionalcomposite materials currently available on the open market.

During at least the last 20-30 years, this has been accomplished bycutting the conventional composite materials into discrete segmentswhich are reoriented by 45° and then spliced back together to form socalled “belts”. The belts are then fabricated into expansion joints,with the warp and fill yarns of the load bearing components arranged ona bias with respect to the expected directions of major stress.

This procedure was reasonably suited to the earlier composite materials,which typically comprised single plies of woven fiberglass coated withrubber. Splicing was easily achieved at relatively low temperatures.However, with the enactment of more aggressive air pollution legislationin the late 1960's and early 1970's, there arose a need for moresophisticated composite materials, with greater resistance to chemicalattack and with a greater ability to span wider gaps between equipmentcomponents.

To meet these demands, more complex rubber composites came on themarket, with fluoroelastomer coatings and multiple layer constructionscontaining two or more woven fabric plies. These more complex compositeconstructions could not readily be subdivided and spliced back togetherto achieve a bias orientation of the woven fabric load bearingcomponents. Thus, bias orientation remained largely limited to thefabrication of expansion joints from the earlier composite materials.

In the 1980's and 1990's, composite expansion joint materials combiningwoven fabric load bearing components with perfluoroplastics such aspolytetrafluoroethylene (PTFE) began acquiring a meaningful marketshare. However, splicing of these materials involved new fabricationprocedures requiring the use of irons heated to elevated temperatures onthe order of 725° F. Such procedures were unfamiliar to the expansionjoint industry. Thus, very little bias production of expansion jointsemploying these PTFE based composites took place, and then only bycutting the materials into segments which were then reoriented on a biasand spliced back together, as was done earlier with the simple rubberbased products.

In recent years, a significant and increasing amount of new powergeneration is being based worldwide on gas and diesel turbines. Thisequipment operates at much higher temperatures, with an attendantincrease in thermally induced movement between equipment components.This has prompted the development of even more complex fluoropolymerbased composite materials, typically comprising PTFE coated woven fabricsubstrates combined with sophisticated corrosion barriers, thermalbarriers and other associated components in multi layer laminatedcomposites.

To date, use of these more sophisticated composite materials in biasoriented configurations has been limited because conventional techniquesfor doing so dictate that the entire composite must be cut through inorder to provide segments which can be reoriented and reassembled bysplicing. The procedures for splicing the individual composite plies ina manner that retains their continuity are exceedingly difficult andoften unreliable. Failure to properly splice the corrosion and/orthermal barrier components can result in the fabrication of flue ductseals which fail prematurely in service.

Use of these materials without arranging their fabric substrates on abias has led to other problems, particularly in flue duct sealsoperating at very high temperatures, where movement between equipmentcomponents is most pronounced. For example, the inability of suchcomposite materials to readily elongate or stretch can lead to theformation of severe creases and/or wrinkles. When wrinkles develop, theresulting folds lose the cooling effect of ambient air. This in turn canproduce “hot spots” or burned areas that will require replacement of theexpansion joint within a very short period.

Accordingly, it is an object of the present invention to provide aflexible composite expansion joint material having as its load bearingcomponent a fluoropolymer containing woven fabric substrate which hasbeen segmented and reoriented into a bias configuration, withoutattendant disruption or compromise in the continuity and integrity ofassociated fluid corrosion barrier and/or thermal barrier components.

A further objective of the present invention is the provision of animproved method for producing the aforesaid expansion joint material asroll goods for use in the fabrication of flue duct seals.

BRIEF SUMMARY OF THE INVENTION

A flexible composite expansion joint material is formed by laminatingtogether a load bearing component comprising a fluoropolymer containingwoven fabric substrate with at least one fluoropolymer fluid corrosionbarrier component and/or a nonfluoropolymer thermal barrier component.The fluoropolymer containing fabric substrate is initially subdividedinto plural segments, each having mutually perpendicular warp and fillyarns. The substrate segments are then reoriented at 45° angles andarranged successively in a longitudinally extending assembly, with thewarp and fill yarns of each substrate segment arranged on a bias, i.e.,extending obliquely with respect to the assembled length. The assemblyof substrate segments is overspread with one or more other components ofthe composite, including, inter alia, fluoropolymer fluid corrosionbarrier film components and/or nonfluoropolymer thermal barriercomponents. The successive fabric substrate segments are splicedtogether and integrally joined to the other composite components bylamination under conditions of elevated temperature and pressure. Thecontinuity and integrity of the latter components is thus unaffected bythe separate subdivision, reorientation and reassembly of the fabricsubstrate segments, which takes place prior to their combination withother components of the composite.

These and other objects, features and advantages of the presentinvention will hereinafter be described in greater detail with referenceto the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a fluoropolymer coated woven fabric substrateuseful as the load bearing component of a flexible expansion jointmaterial in accordance with the present invention;

FIG. 2 is a view similar to FIG. 1 showing the fabric substratesubdivided into a plurality of segments;

FIG. 3 shows the fabric substrate segments of FIG. 2 reoriented andreassembled into a longitudinally extending assembly, with the warp andfill yarns of each segment arranged on a bias;

FIGS. 4a and 4 b are enlarged partial sectional views taken on line 4—4of FIG. 3 and showing alternative splicing arrangements;

FIG. 5 is a view similar to FIGS. 4a and 4 b showing another splicingarrangement; and

FIGS. 6-9 are cross sectional views diagrammatically depicting differentcomposite constructions in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference initially to FIG. 1, a load bearing component comprisinga fluoropolymer containing woven fabric substrate is generally depictedat 10. The substrate is flexible and includes mutually perpendicularwarp and fill yarns indicated typically at 12, 14. Such woven fabricsare considered to be “high modulus materials” due to their wovenconstruction, which resists stretching or elongation in the direction oftheir warp or fill yarns. The fluoropolymer content of the fabricsubstrate is preferably achieved by coating, but lamination andcalendering are other possible alternatives.

In accordance with the present invention, and as shown in FIG. 2, thesubstrate 10 is initially subdivided into a plurality of segments 10′,each segment preferably being in the form of a parallelogram withopposite sides “a”, “b” forming oblique angles. The parallelograms maydefine either rhomboids, where only the opposite sides are equal, orrhombuses where all sides are equal.

As shown in FIG. 3, the substrate segments 10′ are then reoriented by45° and rearranged successively with overlapping adjacent edge regionsto form a longitudinally extending assembly 16. The warp and fill yarns12, 14 of each reoriented segment 10′ thus extend obliquely with respectto the length of the assembly 16.

FIGS. 4a and 4 b illustrate alternative splicing arrangements for theoverlapping edge regions. In FIG. 4a, the edge regions are laminateddirectly to one another by means of the fluoropolymer coating on thewoven substrate. In FIG. 4b, a melt bondable adhesive strip 18 isinterposed between the overlapping edge regions to thereby facilitatelamination.

Another splicing arrangement is disclosed in FIG. 5. Here, the adjacentedge regions of the successive substrate segments are placed in anabutting relationship. The resulting seam is covered by a melt bondableadhesive strip 18 and a strip 20 of the fabric substrate material.Alternatively, the adhesive strip 18 may be eliminated, with thefluoropolymer coating on the strip 20 and abutting segments 10′ servingto effect the bond during lamination. The strip 20 may comprise coatedor laminated fluoropolymer containing textile products other than thefabric substrate material.

In each of the aforesaid splicing arrangements, the materials are bondedtogether under conditions of elevated temperature ranging from 660 to900° F., preferably between 660-770° F., and elevated pressures above 1p.s.i., with the preferred pressure range being between about 40 to 60p.s.i. Typical lamination times range between 20-180 seconds, dependingon the structure and thickness of the composite. The segments 10′ can bejoined either before or after they are combined with other compositecomponents.

The reoriented and sequentially arranged substrate segments 10′ are thenoverspread by and laminated to other composite components in variouscombinations. For example, in FIG. 6, the woven fabric substrate 10 isoverspread by a fluoropolymer fluid corrosion barrier component 22 toform a two ply construction. In FIG. 7, another two ply construction isshown where the woven fabric substrate 10 is overspread by a thermalbarrier component 24. In FIG. 8, a three ply construction includes thefluid corrosion barrier component 22 with the fabric substrate 10 andthe thermal barrier component 24 on opposite sides. In FIG. 9, thefabric substrate 10 is overspread on opposite sides with a fluidcorrosion barrier component 22 and a thermal barrier component 24.

As noted previously, the reoriented successively arranged fabricsubstrate segments 10′ may be laminated together at their spliced jointseither prior to being assembled with other composite components in theexamples shown in FIGS. 6-9, or after being assembled with those othercomponents.

The woven fabric substrate 10 may be produced from various materials,including, inter alia, fiberglass, amorphous silica, graphite,polyaramides including Kevlar and Nomex, PBI (polybenzimadazole),ceramics and metal wires, and combinations thereof. Fiberglass is thepreferred substrate material.

With the exception of metal wires, the same materials also may beemployed to produce the thermal barrier components 24. The thermalbarrier components may be woven or nonwoven. Again, fiberglass is thepreferred material for the thermal barrier components.

Fluoropolymers useful in the composite expansion joint material of thepresent invention may be selected from those known to those skilled inthe art, as described for example in U.S. Pat. No. 4,770,927(Effenberger et al.), the disclosure of which is herein incorporated byreference in its entirety.

Commercially available fluoropolymer products useful with the presentinvention include the following:

Perfluoroplastics

PTFE—Daikin-Polyflon; Dupont Teflon; ICI Fluon; Ausimont Algoflon

FEP—Daikin Neoflon; Dupont Teflon

PFA—Daikin Neoflon; Dupont Teflon; Ausimont Hyflon

MFA—Ausimont Hyflon

Fluoroelastomers

Dupont Viton

3M Fluorel

Ausimont Tecnoflon

Daikin Daiel

Asahi Glass Aflas

Perfluoroelastomers

Dupont Kalrez

Daikin Perfluor

The fluoropolymers of the present invention may include fillers,pigments and other additives, examples of which include titaniumdioxide, talc, graphite, carbon black, cadmium pigments, glass, metalpowders and flakes, and other high temperature materials such as sand,fly ash, etc.

EXAMPLE 1

A flexible composite expansion joint material was produced as acomposite comprising a fluoropolymer coated woven fabric substrate 10, afluoropolymer fluid corrosion barrier component 22 and anonfluoropolymer thermal barrier component 24 arranged in theconfiguration shown in FIG. 8, with the fabric substrate 10 comprisingsubdivided segments reoriented at a 45° bias and arranged withoverlapping edges as shown in FIG. 3, and with the overlapping edgesspliced with intermediate melt bondable adhesive strips 18 as shown inFIG. 4b.

The substrate 10 was a 20″ wide web of TEXCOAT™ 1400, a 32 oz/sq ydwoven fiberglass fabric with a basket weave and a yarn count of 24×26coated on both sides with PTFE and supplied by Textiles CoatedInternational (“TCI”) of Amherst N.H. The total weight of the TEXCOAT™1400 product was 48 oz/sq yd, with the PTFE coating totaling 16 oz/sqyd. The PTFE dispersion was ALGOFLON D60G supplied by Ausimont U.S.A. ofThorofare, N.J.

The fluid corrosion barrier component 22 was an unsintered 0.004″ thickextruded PTFE film supplied by DeWal Corporation of Saunderstown, R.I.

The thermal barrier component 24 was BGF Mat, a ½ thick needledfiberglass insulation mat with a weight of 54 oz/sq yd, supplied by BGFIndustries of Greensboro, N.C. A 1.0 oz/sq yd PTFE coating was appliedto the side of the insulation mat being laminated to the fluid corrosionbarrier component 22.

The adhesive strips 18 comprised 0.003″ unsintered PTFE film.

The TEXCOAT™ 1400 web was cut into 45°/135° rhomboids with sidedimensions a, b of 28″ and 40″. The segments were reoriented to placetheir warp and fill yarns on a bias, and were reassembled with theiredges “a” overlapping by 2.0″, and with single plies of the adhesivestrips 18 interposed therebetween. The assembly of reoriented substratesegments was overspread with the fluid corrosion barrier component 22,which in turn was overspread by the thermal barrier component 24. Thestacked materials were laminated at 715° F. for 135 seconds at apressure of 40 p.s.i.

The finished product weighed approximately 108 oz/sq yd. The productwidth was 28.4″, with the spacing between overlapped splices being28.2″. The fluid corrosion barrier component 22 and the thermal barriercomponent 24 were each continuous. The product displayed excellentcomponent-to-component adhesion and good flexibility.

EXAMPLE 2

Another flexible composite expansion material was produced in theconfiguration shown in FIG. 6.

The substrate 10 was a 7″ wide 18 oz/sq yd fiberglass fabric having a27×14 basket weave and a 16 oz/sq yd PTFE coating supplied by TCI underthe trade name TEXCOAT™ 700. The fluid corrosion barrier was a 0.004″thick extruded unsintered PTFE film supplied by TCI under the trade nameTEXFILM™ 704.

The substrate was cut into two 45°/135° rhomboid shaped segments withside dimensions a, b, of 9″ and 10″. The segments were reoriented at a45° bias with adjacent edges overlapped by 1.5″ as shown in FIG. 3. Meltbondable adhesive strips 18 were interposed between the overlappededges, as shown in FIG. 4b. The strips 18 comprised 5 mil PFA films (500LP; E.I. Dupont, Wilmington, Del.)

The fluid corrosion barrier component 22 was TCI's LFP 2109, a three plycomposite of 0.003″ thick uniaxially oriented unsintered PTFE filmsarranged in accordance with the teachings of U.S. Pat. No. 5,466,531.

The stacked components 10, 22 were laminated at 715° F. for 105 secondsat a pressure of 40 p.s.i. The finished product weighed approximately 38oz/sq yd. The fluid corrosion barrier component 22 was continuousthroughout the product length and covered the 1.5 splice areacompletely. The splice was well sealed and very flexible.

EXAMPLE 3

Another composite expansion joint material was produced in theconfiguration shown in FIG. 6. The woven fabric substrate was againTEXCOAT™ 1400 subdivided into three 45°/135° rhomboid-shaped segmentsreoriented on a 45° bias and arranged with abutting edges as shown inFIG. 5. The abutting edges were covered with 3 wide strips 20 ofTEXCOAT™ 1400, with a 5 mil PFA film interposed therebetween as the meltbondable adhesive 18. The fluid corrosion barrier component 22 comprisedthree plies of unsintered 0.003″ PTFE film. The stacked components werelaminated at 715° F. for 105 seconds at a pressure of 40 p.s.i.

The finished product weighed approximately 62 oz/sq yd. The fluidcorrosion barrier component was continuous over the length of theproduct. The splices were well sealed and very flexible.

EXAMPLE 4

A flexible composite expansion joint material was manufactured in theform of FIG. 9. The woven fabric substrate, TCI's TEXCOAT™ 1400, wassubdivided into two 45°/135° rhomboid-shaped segments reoriented on a45° bias and arranged with overlapping edges as shown in FIG. 4B. Thedimensions of the rhomboid-shaped segments were 13.4″×14.1″. A 0.003″unsintered PTFE film was used as the melt bondable adhesive strip 18.

A 0.004″ thick unsintered PTFE film was placed on one side of theTEXCOAT™ 1400 product. A ½″ fiberglass insulation mat with a PTFEcoating was placed on the other side of the TEXCOAT™ 1400 product.

The stacked components were laminated at 715° F. for 135 seconds at apressure of 40 p.s.i. The finished laminated composite weighedapproximately 110 oz/sq yd. The width of the finished product was 9.5″.The composite displayed a continuous thermal barrier on one side of thefabric substrate and a continuous fluid barrier on the other side. Boththe thermal barrier and the fluid barrier revealed excellent bonds inthe overlapping splice area.

EXAMPLE 5

A flexible composite expansion joint material was manufactured in theform of FIG. 7. A woven fabric substrate comprising TCI's TEXCOAT™ 1400was subdivided into three 45°/135° rhomboid-shaped segments reorientedon a 45° bias and arranged with overlapping edges as shown in FIG. 4A.The segment dimensions were 28.2″×15″ No adhesive was used to seal theoverlap splices. A ½″ thick fiberglass insulation mat with a PTFEcoating was placed on one side of the TEXCOAT™ 1400 product.

The stacked components were laminated at 715° F. for 150 seconds at apressure of 40 p.s.i. The completed flexible laminate contained wellbonded splices and a continuous thermal barrier. The 20″ wide expansionjoint material weighed around 106 oz/sq yd.

In light of the foregoing, it will now be understood by those skilled inthe art that the expansion joint materials of the present invention havea unique “pre-biased” construction achieved by segmenting andreorienting only the woven fabric substrate serving as the load bearingcomponent. The continuity and integrity of the other components of thelaminated composite remain unaffected. The expansion joint materials ofthe present invention are ideally suited for supply as roll goods to theexpansion joint industry. Such materials may be readily incorporatedinto expansion joints, with minimum splicing, and with the bias formatof the load bearing components enabling the materials to readilyelongate when stressed during service.

I claim:
 1. A flexible composite expansion joint material comprising:plural segments of a fluoropolymer containing woven fabric substrate,said substrate having mutually perpendicular warp and fill yarns, saidsegments being arranged successively in a longitudinally extendingassembly with said warp and fill yarns extending obliquely with respectto the length of said assembly; and at least one other componentextending over the length of said assembly, successive segments of saidassembly being spliced together and integrally joined to said othercomponent by lamination under conditions of elevated temperature andpressure.
 2. The expansion joint material of claim 1 wherein said othercomponent is a fluoropolymer fluid corrosion barrier.
 3. The expansionjoint material of claim 1 wherein said other component is anonfluoropolymer thermal barrier.
 4. The expansion joint material ofclaim 1 wherein said fluoropolymer is blended with fillers or additivesselected from the group consisting of graphite, carbon black, titaniumdioxide, talc, cadmium pigments, glass, metal powders and flakes, andsand, fly ash and other like high temperature mineral materials.
 5. Theexpansion joint material of claim 1 wherein said fabric substrate iswoven from materials selected from the group consisting of fiberglass,amorphous silica, graphite, polyaramides, polybenzimadazole, ceramics,metal wires and combinations thereof.
 6. The expansion joint material ofclaim 1 wherein said segments define parallelograms with oblique angles.7. The expansion joint material of claim 6 wherein said segments definerhomboids.
 8. The expansion joint material of claim 6 wherein saidsegments define rhombusses.
 9. The expansion joint material of claim 6wherein said successively arranged segments have overlapping edgeregions.
 10. The expansion joint material of claim 9 wherein a meltbondable adhesive is interposed between said overlapping edge regions.11. The expansion joint material of claim 6 wherein said successivelyarranged segments have abutting edge regions overlapped by connectingstrips.
 12. The expansion joint material of claim 11 wherein a meltbondable adhesive is interposed between said edge regions and saidconnecting strips.
 13. The expansion joint material of claim 10 or 12wherein said melt bondable adhesive is a fluoropolymer.
 14. Theexpansion joint material of claim 1 wherein said warp and fill yarnsextend at 45° angles with respect to the length of said assembly. 15.The expansion joint material of claim 3 wherein said nonfluoropolymerthermal barrier component is laminated to said assembly by means of afluoropolymer melt bondable adhesive.
 16. The expansion joint materialof claim 15 wherein said fluoropolymer melt bondable adhesive is appliedas a coating to one surface of said thermal barrier component.
 17. Theexpansion joint material of claim 3 wherein said thermal barriercomponent is selected from the group consisting of woven or nonwovenfiberglass, amorphous silica, graphite, polyaramides, polybenzimadazoleand ceramic.
 18. The expansion joint material of claim 1 wherein saidother component comprises a fluoropolymer fluid corrosion barrier, andanother component comprises a nonfluoropolymer thermal barrier.
 19. Theexpansion joint material of claim 18 wherein said fluoropolymer fluidcorrosion barrier component and said thermal barrier component arelaminated to opposite sides of said assembly.
 20. The expansion jointmaterial of claim 18 wherein said assembly and said thermal barriercomponent are laminated to opposite sides of said fluid corrosionbarrier component.
 21. The expansion joint material of claim 1, 13 or 15wherein said fluoropolymer is a perfluoroplastic.
 22. The expansionjoint material of claim 21 wherein said perfluoroplastic is blended witha fluoroelastomer.
 23. The expansion joint material of claim 21 whereinsaid perfluoroplastic is selected from the group consisting ofpolytetrafluoroethylene, fluorinated ethylene propylene andperfluoroalkoxy.
 24. The expansion joint material of claim 23 whereinsaid perfluoroplastic is polytetrafluoroethylene.
 25. The expansionjoint material of claim 2 wherein said fluoropolymer fluid corrosionbarrier comprises at least one PTFE film which is unsintered prior tolamination.